The aim of this research is to study the coagulation mechanism by following the change in rheological properties of blood with time. The goal is to determine systematically the effect of blood coagulation factors, anticoagulants, fibrinolytic agents, and fluid shearing on the viscosity and elasticity of the blood as the clotting and fibrinolysis proceeds. By measuring specific material properties, we should be able to examine the polymerization and "crosslinking" reactions and gain some basic knowledge about the coagulation and fibrinolytic reactions and their effect on clot structure. Information about the fundamental biochemical structure of fibrin clots, the kinetics of formation of clot structure, and further knowledge on the platelet-fibrin interaction during fibrin polymerization will be attained using the combination of rheological and biochemical techniques proposed. The results should be useful in evaluating possible changes in the coagulation mechanism brought about by mechanical trauma experienced in circulatory assist devices. These results may also form a basis for screening or monitoring hemorrhagic or hyper-coagulable patients, either from natural blood defects or anticoagulation therapy.